Introduction

The appearance of the mid-face – in particular the periorbital region – marks the cornerstone of facial attractiveness, an important factor in social and interpersonal interactions. As ‘window to the soul’, the eye can express a variety of emotions and is one of the most compelling features of any face. The use of botulinum toxin (BoNT) in the periocular area has a long history; indeed, the discovery of the toxin’s benefits were first noted in patients treated for strabismus and blepharospasm, and it has since been used therapeutically in the eyelid for the treatment of numerous other blepharospastic conditions and systemic diseases affecting the periorbital area, such as facial palsies and lid retraction in thyroid ophthalmopathy. Since then, BoNT has become an important part of the armamentarium for the cosmetic or functional improvement of the periorbital area, alone or in combination with other rejuvenating modalities. However, treatment in the upper and lower lids – the thinnest skin in the human body – requires an in-depth understanding of anatomy and the aging process, appropriate patient selection, and careful attention to individualized treatment.

Anatomy of the eye

Complete knowledge and understanding of both dynamic and volumetric changes in the face, as well as the interaction between and function of various facial musculature and the surrounding soft tissue, are critical to ensuring successful outcomes with the use of BoNT in the periorbital region. Although in-depth examinations of facial anatomy have been published elsewhere, this chapter focuses on the anatomy of the eye relevant to the use of BoNT in the upper and lower eyelids (Fig. 16.1).

Figure 16.1 Periorbital anatomy.

The upper eyelid extends from the eyelid margin to the eyebrow superiorly, with the superior palpebral sulcus (associated with the upper eyelid skin crease) located lengthwise between the medial canthus and the lateral orbital rim, approximately in the range of 8–11 mm superior to the eyelid margin. The lower eyelid extends below the inferior orbital rim to join the cheek. In youth, the inferior palpebral sulcus (lower eyelid fold) is located 3–5 mm from the lower lid margin.

The orbicularis oculi – the sphincter muscle of the eyelids – is a wide, concentric band of muscle comprising the palpebral component, which can be further divided into pretarsal and preseptal portions and is responsible for blinking and gentle eyelid closure, and the orbital component, responsible for forceful lid closure and the production of lateral canthal and lower eyelid rhytides. Superiorly, the orbital component interdigitates with other superficial muscles of facial expression, including the frontalis, corrugator, and the depressor supercilii muscles, laterally it comes into proximity of the overlying fascia of the temporalis muscles, and the muscles of the inferior quadratus labii superioris and zygomaticus complex. Inferiorly, the orbicularis lies flat across the cheek and is considered a part of the superficial musculoaponeurotic system (SMAS), which translates muscle movement into movement of the skin. At the junction of the lower lid with the cheek, the orbicularis oculi muscle forms a direct attachment with the orbital rim at the junction of the palpebral and orbital portions.

Periorbital aging

Aging in the face is most prominent in the mid-facial and periorbital regions, due to both dynamic and volumetric changes. Bony changes and atrophy of subcutaneous soft tissues lead to a loss of cutaneous support, muscles become lax, and skin that was once smooth and youthful becomes rough and dry with irregular pigmentation and uneven texture. As the skin repositions itself over the changing landscape of the face, wrinkles and fine lines begin to appear and become prominent as dynamic turns to static.

Eyelid skin is the thinnest on the body (<1 mm), with sparse underlying subcutaneous fat. Over time, the delicate lids are prone to further thinning and stretching by too-vigorous rubbing or surgical procedures to rejuvenate the area. The lower lid is subject to fat redistribution, laxity, and weakening of the connective tissue. The normally smooth transition from lower lid to cheek becomes more prominent, with puffiness, dark circles, or dermatochalasis under the eye. Orbital laxity, atrophy, and pseudoherniation give the impression of a sunken eye, while radial wrinkles appear on the lateral aspect of the orbit.

Patient assessment and selection

Because successful use of BoNT in the periorbital region demands close attention to anatomical variations and individualized treatment, a thorough evaluation of every patient is mandatory. Comprehensive assessment will include patient education and counseling, medical history, and physical examination of the periorbital region and area to be treated.

Communication between patient and clinician builds trust and ensures that expectations do not exceed realistic outcomes. Evaluation of periorbital concerns in discussion as well as physical examination will avoid post-injection problems. Interviews should address the patient’s current ophthalmic status including the presence of dry eye symptoms as well as the transient nature of BoNT injections, the need for frequent touch-ups, common injection-related side effects, and potential complications. Informed consent is essential.

A complete medical and ophthalmic history is necessary, including previous experiences with rejuvenation procedures, surgery, and any other conditions that might influence treatment plans or outcome. The degree of rhytides and their potential response to treatment can be assessed via the Glogau photoaging scale (Table 16.1). Moreover, the quality of skin around the eye will also determine a treatment plan: patients with excessive skin above the eye, prominent fat pads in the lower lid, septal fat herniation, or severe elastosis (identified by a positive snap test), may require additional rejuvenating procedures such as laser or light-based therapies or even surgery prior to augmentation. All findings (including any sign of ptosis or asymmetry) should be noted and discussed with the patient, and standard digital photographs taken both before and after any treatments. Photographs should display the face in repose and at maximal expression to document changes on animation.

Table 16.1 Wrinkle severity and rejuvenation requirements

^* Based on the Glogau classification of photoaging.

Not everyone is a candidate for BoNT therapy. Aside from general contraindications (Box 16.1), caution should prevail in patients with a history and especially complications related to previous lower eyelid blepharoplasty and injections avoided in patients with lower lid laxity, due to the risk of scleral show, pre-existing conditions that could be worsened by treatment, such as mid-facial paresis or symptomatic dry eyes, stable or progressive muscular dystrophic conditions causing blepharoptosis, or anyone with already-compromised function of the orbicularis oculi.